D&D 5th Edition. It is what it is and naming it something else doesn't change that. They should be proud of that name. It's come a long way. Naming it 5E isn't going to confuse anyone or cause anyone to dislike the game for seeing the name as some sort of hype. Without an iteration signifier, it seems rather like claiming the work of those who came before is trumped by this edition and I don't think the designers want to be saying that.
The false naming makes me wonder if someone thinks they are being clever when they try and disguise the iteration of the game. I recall one employee trying to convince some customers that there wouldn't be a half edition of the game. Of course, there was but they named it something else. What that did was cause confusion in the market, make some customers wonder if that employee thought they were being clever (or worse, lying), and generate additional mistrust for the company (that was already beleaguered with problems).
Just make a D&D 5E RPG that everyone feels is D&D and also that everyone feels is an RPG, and it will bear the 5E part proudly. Now is not the time for clever naming conventions. And you know what? A few years in when there's been enough time to assess how things are going, pull the few core books still out in distributioin and announce in advance to retailers and the customer base that you plan to produce a 5.5E, all up front and open, without any of the tricks usually on display to avoid losing sales (which are lost in other ways by such trickery anyway). This is turning-over-a-new-leaf time. This is we-want-to-be-trusted-again time. Let's not see it blown with clever marketing tricks. Let's see it won through good design, hard work, and honest dealings.